Batteries may be made up of multiple cells in series in order to achieve higher operating voltages. Production tolerances, uneven temperature distribution, differences in the aging characteristics of particular cells, or other differences between the cells can cause decreased performance or premature failure of a battery. For example, during a charging cycle, if the battery has a degraded cell (that is, a cell with a diminished capacity), after the degraded cell has reached its full charge, it may be subject to overcharging until the rest of the cells of the battery reach their full charge. Overcharging the cell may lead to temperature and pressure build up in the cell and may cause damage to the cell, the battery, or even other nearby devices. During discharging, the weakest cell in the battery may have the greatest depth of discharge (i.e., lowest state of charge) and therefore may be completely discharged before the other cells. Generally, once a single cell of a battery has failed, the entire battery must be replaced, which can be expensive and time consuming.